Remember Position of vertical divider between stylesheets, choosing for a custom stylesheet

Changing Css stylesheets for e-books is no one time action. I return to the Css-tab again and again and have to create space for editing the stylesheet each time.

I wish the vertical divider between stylesheets would stay on the far right-hand side when I return to that tab, since the drop down list clearly says I want to create a Custom stylesheet.

Alternatively, a toggle button collapsing the default stylesheet would work.

Keep up the good work!